The invention relates to an apparatus for projecting a multi-colored picture on a projection screen, having a light source that emits heterochromatic light, a color unit arranged following the light source, having a first and a second light modulator arranged following the color unit, and a projection optics where the color unit can be illuminated with the light emitted from the light source and separates light of a first color and directs it on the first light modulator, and separates light of a second color and directs it on the second light modulator, where the light modulators modulate the light shining on them in order to create one color frame each of the multi-colored picture, and where the modulated light is superimposed to form a common luminous beam by means of the color unit, where the luminous beam illuminates the projection optics.
In such an apparatus, as is described in EP 0 734 183 A2, for example, the required focal intercept is very large due to the color unit provided between the projection optics and the light modulators by means of which the color frames are set. This necessitates a very complicated projection optics with numerous lenses which makes projection optics expensive and weighty. In addition, the color unit usually comprises glass elements with dichroic coatings, so that a long glass way exists between the light modulators and the projection optics which has to be passed through by the different-colored light in order to generate the color frames. The result is a transverse achromatic aberration due to the state of dispersion of the glass elements, so that the different color components of a pixel no longer overlap but are situated next to each other in the projection screen. This transverse achromatic aberration has to be compensated for by means of the projection optics, which in turn calls for a complicated structure of the projection optics.
In order to avoid the transverse achromatic aberration, lenses made of optical flint and lenses made of optical crown are combined in order to generate the required achromatization, wherein Flourite is often used which is very difficult to work. This makes the production of the projection optics very complicated. In addition, Fluorit has disadvantageous hygroscopic characteristics that can adversely affect the imaging characteristics of the projection optics over time.
Based on this situation, it is the object of the present invention to improve an apparatus of the above-mentioned kind for projecting a multi-colored picture on a projection screen in such a way that its design is simplified.
Taking an apparatus of the above-mentioned kind for projecting a multi-colored picture on a projection screen, the object is completed by connecting an optics system illuminated with a common luminous beam and having a curved mirror is provided between the color unit and the projection optics, where the optics system generates a multi-colored intermediate image in an intermediate image level arranged in front of the projection optics, where the multi-colored intermediate image is projected by the projection optics on the projection screen as the multi-colored picture.
The invention relates to an apparatus for projecting a multi-colored picture on a projection screen, having a light source that emits heterochromatic light, a color unit arranged following the light source, having a first and a second light modulator arranged following the color unit, and a projection optics where the color unit can be illuminated with the light emitted from the light source and separates light of a first color and directs it on the first light modulator, and separates light of a second color and directs it on the second light modulator, where the light modulators modulate the light shining on them in order to create one color frame each of the multi-colored picture, and where the modulated light is superimposed to form a common luminous beam by means of the color unit, where the luminous beam illuminates the projection optics.
In such an apparatus, as is described in EP 0 734 183 A2, for example, the required focal intercept is very large due to the color unit provided between the projection optics and the light modulators by means of which the color frames are set. This necessitates a very complicated projection optics with numerous lenses which makes projection optics expensive and weighty. In addition, the color unit usually comprises glass elements with dichroic coatings, so that a long glass way exists between the light modulators and the projection optics which has to be passed through by the different-colored light in order to generate the color frames. The result is a transverse achromatic aberration due to the state of dispersion of the glass elements, so that the different color components of a pixel no longer overlap but are situated next to each other in the projection screen. This transverse achromatic aberration has to be compensated for by means of the projection optics, which in turn calls for a complicated structure of the projection optics.
In order to avoid the transverse achromatic aberration, lenses made of optical flint and lenses made of optical crown are combined in order to generate the required achromatization, wherein Flourite is often used which is very difficult to work. This makes the production of the projection optics very complicated. In addition, Fluorit has disadvantageous hygroscopic characteristics that can adversely affect the imaging characteristics of the projection optics over time.
Based on this situation, it is the object of the present invention to improve an apparatus of the above-mentioned kind for projecting a multi-colored picture on a projection screen in such a way that its design is simplified.
Taking an apparatus of the above-mentioned kind for projecting a multi-colored picture on a projection screen, the object is completed by connecting an optics system illuminated with a common luminous beam and having a curved mirror is provided between the color unit and the projection optics, where the optics system generates a multi-colored intermediate image in an intermediate image level arranged in front of the projection optics, where the multi-colored intermediate image is projected by the projection optics on the projection screen as the multi-colored picture.
By providing the optics system that generates the intermediate image (preferably a real intermediate image) in the intermediate image level located in front of the projection optics (the intermediate image level can preferably also be located directly in front of the projection optics), the required focal intercept of the projection optics is much smaller in the apparatus according to the invention than the apparatus of the above-mentioned kind. This also lowers the optical requirements of the projection optics substantially, of course, so that the design of the projection optics is noticeably simplified. The number of required lenses of the projection optics is lower, in particular, which also allows for a weight reduction.
In addition, the projection optics can also be provided and designed entirely independently from the rest of the apparatus, since its task is to image the intermediate image generated in the intermediate image level, and not the picture-generating areas of the light modulators, on the projection screen.
Also, in the apparatus according to the invention, the projection optics may easily be replaced by another projection optics, so that the apparatus according to the invention may be adapted easily to diverse basic conditions, such as a wide angle projection or a projection where the optical axis of the projection optics includes an angle unequal to 90 degrees with the projection screen.
Besides folding of the path of the rays, the curved mirror also contributes to the imaging process, so that therefore the number of optic elements of the optics system may be further reduced.
The light modulators which are preferably reflective light modulators (which advantageously allow the realization of a very compact apparatus) have an image-generating area (rectangular, for instance) with a majority of pixels that can be selected independently from each other, from which the incoming light is being reflected modulated (such as with respect to its angle of reflection or direction of polarization), wherein reflected light is utilized in a first state of modulation for bright pixels, and reflected light in a second state of modulation is utilized for dark pixels, so that hereby pictures (or color frames) are generated on the light modulators or their image-generating areas. The light modulators can be designed in such a way, of course, that light is reflected only by the pixels of the bright picture elements, while no light is emanating from the pixels of the dark picture elements because incidental light is absorbed there.
In a preferred embodiment of the apparatus according to the invention, the optics system is a 1:1 image optics. This preferably means that the intermediate image has the same size as the color frames, which means that the lens diameter of the projection optics can be kept small. In addition, the imaging characteristics of the optics system are best.
In particular, the optics system can be structured such that the color frames in the intermediate image level are imaged reduced in size. This advantageously results in an even smaller design of the aperture of the projection optics and thus also its optical elements, which means that the projection optics can be produced more cost-efficiently and simply. In addition, a reduction in weight is accomplished so that the apparatus according to the invention becomes lighter overall.
The optics system of the apparatus according to the invention is preferably structured symmetrically with respect to the mirror. On the one hand, this results in a reduction of the number of optics elements required within the optics system, since they are being passed through twice. On the other hand, if the optics system is a symmetrical 1:1 imaging optics, the image distortion generated by the optics system is very small and is practically zero in the best-case scenario, thus basically non-existent.
A preferable embodiment of the apparatus according to the invention is such that the mirror of the optics system comprises a spherical curve. In that case, the mirror is easy to produce, which enables a cost-efficient optics system and thus a cost-efficient apparatus for projecting of a multi-colored picture.
In addition, the optics system of the apparatus according to the invention can be a catadioptrics optics (an optics that includes at least one imaging mirror and at least one imaging lens). Such optics allows for particularly good imaging characteristics at a small size with few optics elements, so that an advantageous weight reduction can be accomplished, as well.
In a preferable further embodiment of the apparatus according to the invention, the mirror of the optics system may consist of a reflective coating on a curved boundary surface of a transparent optics element turned away from the optics system. The advantage is that the number of elements of the optics system to be adjusted is reduced, so that it can be produced more quickly. Also, the reflective coating is administered on the boundary surface, thereby not comprising an open silvered boundary surface which could be contaminated easily. This ensures the reflective and imaging characteristics of the optics system to remain constant.
A particularly preferred further development of the apparatus according to the invention is that a third light modulator is arranged following the color unit, wherein the color unit separates a third color from the light emitted by the light source and directs it to a third light modulator, so that a third color frame can be set thereon. Since three light modulators are provided for three different color frames, a brilliant color picture consisting of the superimposed color frames can be generated without a problem.
Color frames in the primary colors red, green, and blue are preferably generated by the light modulators, from which the desired multi-colored picture with a high color brilliance may be generated.
In an embodiment of the apparatus according to the invention, the light modulators are designed in such a way that they modulate the state of polarization, particularly the direction of polarization, of the light shining on them preferably polarized linearly, wherein the light modulators are preferably realized by reflective or transmissive LCD modulators.
This enables the creation of polarization-modulated color frames by the light modulators. In such cases, an analyzer arranged in front of the intermediate image level is provided that can be illuminated with the modulated light from the light modulators, thus causing only light with a pre-determined state of polarization to pass into the intermediate image level. This preferably causes only the light from the picture elements made bright by the light modulators to pass into the intermediate image level and then be projected on the projection screen by the projection optics.
The analyzer is preferably located between the intermediate image level and the optics system, thereby allowing the path of the illuminating rays of the light emitted by the light source that illumines the reflective light modulators, and the path of the projecting rays of the light reflected by the reflective light modulators being imaged into the intermediate image level to be superimposed into the optics system. This allows for a very compact construction of the apparatus according to the invention.
In particular, the light modulator may also be a tilting mirror matrix that includes numerous tilting mirrors provided in lines and columns, wherein the mirrors may be tilted independently from each other in a first and a second tilting position. In that case, the apparatus according to the invention is provided in such a way that the light reflected by the mirrors in the first tilting position reaches the intermediate image level, while the light reflected by the mirrors in the second tilting position-does not reach the intermediate image level. The tilting mirrors advantageously allow for the realization of an apparatus according to the invention, wherein the light illuminating the tilting mirror matrix does not have to be specially polarized, so that the losses incurred by a polarization of the light can be avoided.
The apparatus according to the invention may also advantageously be developed further, such that the optics system consists of a plano-convex lens and a silvered meniscus lens, wherein the boundary surface of the meniscus lens turned away from the plano-convex lens is silvered. The lens diameters are chosen large enough for each lens to be passed through twice in one reflection. In that case, the optics system includes only two optics elements which means that the costs of production and the adjustment needed are minor. Thus, an apparatus according to the invention is provided that can be manufactured very cost-efficiently overall.
It is also possible, of course, to replace the one plano-convex lens with two plano-convex lenses having a smaller diameter, which are then passed through only once for each image. In such cases, the optics system includes three elements, but due to their clearly smaller diameter, the production of the two plano-convex lenses is simpler than the production of the plano-convex lens with a large diameter.
In another advantageous embodiment of the apparatus according to the invention, the optics system includes not only a concave, but also a convex mirror. Thus, an optics system can be realized by no more than reflecting mirrors, so that no lenses manufactured in a complicated manner and from expensive materials are needed. This, too, allows for a more cost-effective realization of the apparatus according to the invention.
In addition, the optics system of the apparatus according to the invention may be such that it images not only an illuminated area generated with light from the light source on the light modulators, but also images the color frames in the intermediate image level. In that case, the optics system entirely assumes the function of an otherwise separate lighting optics that is provided between the luminous area and the light modulators and serves to illuminate the light modulators, so that no lighting optics has to be included in the apparatus according to the invention. This allows for a compact realization of the apparatus according to the invention.
The apparatus according to the invention can also be further developed such that it includes a control unit that triggers the light modulators on the basis of pre-determined picture data in order to generate the desired color frames with the light modulators.